Sensor connection means

ABSTRACT

The invention relates to a sensor adapted for electrical connection to a power source having an electrical contact means ( 3 ). The sensor has a first insulating substrate ( 1 ) carrying a first electrode ( 2 ) and a second insulating substrate ( 7 ) carrying a second electrode ( 6 ). The electrodes are disposed to face each other in spaced apart relationship, sandwiching a spacer ( 4 ) therebetween. A first cut-out portion extends through the first insulating substrate ( 1 ) and a spacer ( 4 ) to expose a first contact area ( 23 ) on the second insulating substrate ( 7 ). This permits the electrical contact means ( 31 ) to effect electrical connection with the first contact ( 23 ) which in turn is in electrically conductive connection with the second electrode ( 6 ). A similar contact arrangement may be disposed on the opposite side of the sensor.

RELATED APPLICATIONS

[0001] This application is a continuation application of InternationalPatent Application No. PCT/AU98/00184, internationally filed Mar. 20,1998, and claiming priority from Australian Provisional PatentApplication No. PO 5813, filed Mar. 21, 1997.

TECHNICAL FIELD

[0002] This invention relates to disposable electrochemical sensors ofthe type used for quantitative analysis, for example, of glucose levelsin blood, for pH measurement, or the like. More particularly theinvention relates to means for electrical connection of such sensors toa measuring apparatus.

BACKGROUND ART

[0003] U.S. Pat. No. 5,437,999 discloses an electrochemical sensor ofthe kind which in use is electrically connected with a power source. Thesensor is constructed from two spaced apart printed circuit boards eachhaving a metal layer on one side and disposed so that the metal layersare facing each other in spaced apart relationship. The metal layers arephotolithographically treated to define electrode areas which form partof a cell. At one end of the assembly the electrode substrates are cutto provide laterally spaced protruding tabs bearing the metal layer. Theexposed metal surfaces of the tabs act as contact pads, each contact padbeing electrically connected with a corresponding electrode. The contactpads in turn engage contact prongs connected to a power source andprovide electrical connection between the sensor and a power source.

[0004] The arrangement of U.S. Pat. No. 5,437,999 suffers from thedisadvantages that the substrate is required to be of considerablerigidity in order to ensure satisfactory and reliable electricalcontact. Moreover the user is often left uncertain as to whether asensor has satisfactorily been connected with the power source.

[0005] In co-pending applications PCT/AU96/00207, PCT/AU96/00365,PCT/AU96/00723 and PCT/AU96/00724 there are described various very thinelectrochemical cells. Each cell is defined between facing spaced apartelectrodes which are formed as thin metal coatings (for example sputtercoatings) deposited on thin inert plastic film (for example 100 micronthick PET). The electrodes are separated one from the other by a spacerof thickness of for example 500 μm or less.

[0006] The connection arrangement of U.S. Pat. No. 5,437,999 is notsuitable for use with the extremely thin sensor devices of the kinddiscussed in our co-pending applications in view of the flexibility ofthe insulating electrode carriers. In general, it is desirable that thedisposable sensor be capable of simple, quick, reliable and effectiveconnection with the power source in the measuring device by unskilledusers. It is an object of the present invention to overcome orameliorate at least one of the disadvantages of the prior art, or toprovide a useful alternative.

DESCRIPTION OF THE INVENTION

[0007] According to a first aspect, the invention provides a sensoradapted for electrical connection with a power source having firstcontact means, the sensor comprising:

[0008] a first insulating substrate carrying a first electrode and asecond insulating substrate carrying a second electrode, said electrodesbeing disposed to face each other in spaced apart relationship,

[0009] a first cut-out portion extending through said first insulatingsubstrate and a spacer to expose a first contact area on the secondinsulating substrate to permit a first contact means to effectelectrical connection with the first contact area disposed on the secondinsulating substrate, the first contact area being in electricallyconductive connection with the second electrode.

[0010] The first contact area may be maintained at a predetermined depthfrom the first insulating substrate.

[0011] According to a second aspect, the invention provides a sensoraccording to the first aspect further comprising a second cut-outportion extending through said second insulating substrate and the, oranother, spacer to expose a second contact area on the first insulatingsubstrate to permit a second contact means to effect electricalconnection with a second contact area disposed on the first insulatingsubstrate, the second contact area being in electrically conductiveconnection with the first electrode.

[0012] The second contact area may be maintained at a predetermineddepth from the second insulating substrate.

[0013] According to a third aspect, the invention also provides asensing system comprising a sensor according to the first or secondaspects and a sensing apparatus including a first contact means and/orsecond contact means adapted to effect electrical contact with the firstand second contact areas respectively.

[0014] “Comprising” as herein used is used in an inclusive sense, thatis to say in the sense of “including” or “containing.” The term is notintended in an exclusive sense (“consisting of” or “composed of”).

[0015] In preferred embodiments the insulating substrate is made of aflexible insulating material. The second electrode and the first contactarea are formed from a unified layer of metal deposited on the firstsubstrate, and more preferably deposited by being sputter coatedthereon. Suitable metals include, but are not limited to palladium,gold, platinum, iridium, and silver. Carbon may also be used. Desirablythe contactor is a metal contactor which is resiliently biased to extendthrough the first cut-out portion to make contact with the metal firstcontact area on the second substrate. In highly preferred embodimentsthe contactor is adapted for click engagement with the cut-out portionwhich extends through the first insulating substrate and the spacer.

[0016] With a connector according to the current invention the spacerlayer provides extra strength. A rigid connector can therefore be formedusing flexible materials. This allows a wider range of materials to beutilized. An audible confirmation of connection can also be simplyprovided by the current invention unlike the connector described in U.S.Pat. No. 5,437,999.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will now be described by way of example only withreference to the accompanying drawings in which:

[0018]FIG. 1 shows a first embodiment of a sensor according to theinvention in plan view.

[0019]FIG. 2 shows a scrap side elevation of the sensor of FIG. 1 incross-section on line 10-10.

[0020]FIG. 3 is a diagrammatic enlargement showing a part of the sensorof FIG. 2 in engagement with contacts.

[0021]FIG. 4 shows an end elevation of the sensor of FIG. 3 in sectionon line A-A.

[0022]FIG. 5 shows a second embodiment of the invention in plan view.

[0023]FIG. 6 shows a cross-section of the embodiment of FIG. 5 in endelevation when viewed on line C-C.

[0024]FIG. 7 shows a cross-section of the embodiment of FIG. 5 in sideelevation on line D-D.

[0025]FIG. 8 shows a third embodiment of the invention in plan view.

BEST MODES FOR CARRYING OUT THE INVENTION

[0026] With reference to FIGS. 1 to 3 there is shown a first embodimentof an electrochemical sensor. The sensor comprises a polyester spacer 4approximately 25 mm×5 mm and 100 microns thick and having a circularaperture 8 of 3.4 mm diameter. Aperture 8 defines a cylindrical cellwall 10. Adhered to one side of spacer 4 is a first insulating substratepolyester sheet 1 having a first coating of palladium 2. The palladiumwas sputter coated on sheet 1 at between 4 and 5 millibar pressure in anatmosphere of argon gas to give a uniform coating thickness of about100-1000 angstroms. Sheet 1 is adhered by means of adhesive 3 to spacer4 with palladium coating 2 adjacent spacer 4 and covering one side ofaperture 8.

[0027] A second insulating substrate 7 consists of a polyester sheethaving a second sputter coating 6 of palladium adhered by means ofcontact adhesive 5 to the other side of spacer 4 and covering theopposite side of aperture 8. There is thereby defined a cell havingcylindrical side wall 10 and closed at one cylinder end by a firstelectrode of palladium metal 2. The other cylinder end wall is a secondelectrode formed from palladium 6. The assembly is notched at 9 toprovide a means for admission of a solution to the cell, and to allowair to escape.

[0028] Adjacent one end 20 a cut-out aperture 21 pierces firstinsulating layer 1 and first metal layer 2. In the present examplecut-out 21 is oval-shaped. A corresponding cut-out portion 22 in spacer4 is in registration with cut-out 21. FIG. 3 shows a side elevationcross-section of sensor 1 inserted into a receiving slot formed in part30 of measuring apparatus and to which is mounted a first resilientcontactor 31 and a second resilient contactor 32. Upon insertion ofsensor end 20 into the slot, contactor 31 rides over the outer surfaceof insulating layer 1 and clicks into the well formed by apertures 21and 22 to engage a first contact area portion 23 of metal layer 6. Firstcontact area 23 is a portion of the same metal layer 6 deposited oninsulating layer 7 from which the second electrode is formed and istherefore in electrically conductive communication with the secondelectrode area of cell 8. Contact area 23 is in effect defined by thediameter of cut-out 20 of spacer 4 in the present example.

[0029] In the embodiment shown in FIG. 1 a second circular cut-outportion 25 spaced further from edge 20 than aperture 21 extends throughsecond insulating layer 7 and second metal layer 6. A cut-out portion 26(see FIG. 2) of spacer 4 corresponds with an registers with cut-outportion 25 of insulating layer 7. Referring again to FIG. 3, in use thesensor is configured to permit a second resiliently biased contactor 32to extend through the well defined by cut-out portions 25 and 26 wherebyresilient contactor 32 engages and makes electrical contact with metallayer 2 at 27 and thereby with the first electrode 2 of cell 8.

[0030] Resilient connectors 31 and 32 are arranged in a slot 30 of themeasuring device and are electrically connected in a measuring circuit.In use, the sensor is inserted into slot 30 with edge 20 leading. Thefirst resilient contactor 31 rides over the end margin of the sensor 1until it encounters first aperture 21, 22 whereupon it click engageswith the opening and makes electrical contact with the first contactarea 23 of metal layer 6. Slight additional insertion of sensor 1 inslot 30 causes the second contactor 32 to click engage with the secondaperture 25, 26 and make contact with second contact area 27 of metallayer 2.

[0031] Spacer 4 surrounds both apertures and ensures that, despite theintrinsic flexibility of the insulating layers and the thinness of thesensor, electrical contact can be made with reliable precision.

[0032] A second embodiment of the invention is shown in FIGS. 5, 6 and 7wherein parts corresponding in function to corresponding parts of theembodiment of FIGS. 1 and 2 are identified by corresponding numerals.The major difference between the second embodiment and the first is thatin the second embodiment cut-out portions 21, 22 are cut from one sideedge of sensor 1 while cut-out portions 25, 26 are cut out from theopposite side edge of the sensor 1. In this case contactors 31 and 32are spaced laterally and click substantially simultaneously into theirrespective cut-out opening. The cut-out openings are surrounded on threesides by spacer 4, the fourth side being exposed at respective edges ofthe sensor.

[0033] Although in the embodiment shown in FIGS. 5, 6 and 7 the openingsare at a corresponding distance from end 20 in other embodiments theycould be spaced in the longitudinal direction as is the case in thefirst described embodiment. This ensures that contact is only made whenthe sensor is inserted in a correct orientation and ensures correctpolarity.

[0034] A third embodiment is shown schematically in FIG. 8. In this casethe openings take the form of slots 21, 25 extending longitudinally fromedge 20. For preference spacer 4 extends around all edges of openings 21and 25 of FIG. 8 but in a less preferred embodiment spacer 4 onlyextends on three sides of slots 21 and 25 in which case click engagementis not obtained or is obtained only if the contacts extend from theopposite direction. However, the advantage that the contact pad area ofthe sensor is at a predetermined dimension from the opposite face ismaintained. If desired the slots can differ in length and co-operationwith contacts spaced longitudinally so that contact with both contactsrequires correctly orientated insertion of the sensor.

[0035] It will be understood that both construction materials anddimensions are given merely by way of example and that sensors of adiffering design or construction may utilize the invention. One, two ormore than two contacts may be provided by the means shown. The inventionextends to include a power source or measuring device when connected toa sensor by the means described. Any suitable form of contactor may beused with sensors according to the invention.

What is claimed is:
 1. A sensor adapted for electrical connection with apower source having a contactor, the sensor comprising: a firstinsulating substrate carrying a first electrode and a second insulatingsubstrate carrying a second electrode, said electrodes being disposed toface each other in spaced apart relationship, a first cut-out portionextending through said first insulating substrate and a spacer to exposea first contact area on the second insulating substrate to permit thecontactor to effect electrical connection with the first contact areadisposed on the second insulating substrate, the first contact areabeing in electrically conductive connection with the second electrode.2. A sensor according to claim 1 wherein the first contact area ismaintained at a predetermined depth from the first insulating substrate.3. A sensor according to claim 1 wherein the second contact area ismaintained at a predetermined depth from the second insulatingsubstrate.
 4. A sensor according to claim 1 wherein each insulatingsubstrate is made of a flexible insulating material.
 5. A sensoraccording to claim 4 wherein the flexible insulating material ispolyester.
 6. A sensor according to claim 1 wherein each electrode andits respective contact area are formed from a layer of metal depositedon the insulating substrate.
 7. A sensor according to claim 6 whereinthe metal is selected from the group consisting of palladium, gold,platinum, iridium and silver.
 8. A sensor according to claim 6 whereinthe metal is 10-1000 nanometers thick.
 9. A sensor according to claim 6wherein the layer of metal is deposited on the substrate by sputtercoating.
 10. A sensor according to claim 1 wherein each electrode andits respective contact area are formed from carbon.
 11. A sensoraccording to claim 1 wherein the cut-out portions are laterally spacedapart relative to the longitudinal axis of the sensor.
 12. A sensoraccording to claim 1 wherein the cut-out portions are longitudinallyspaced relative to the longitudinal axis of the sensor.
 13. A sensoraccording to claim 1 wherein the cut-out portions are laterally andlongitudinally spaced relative to the longitudinal axis of the sensor.14. A sensor according to claim 1 wherein at least one of the substrateor spacer extends around the entire periphery of the cut-out portion.15. A sensor according to claim 1 wherein the cut-out portion is adaptedfor click engagement with a contactor.
 16. A sensor according to claim 1wherein the cut-out portion is cut from an edge of the sensor such thatthe cut-out portion is open on at least one edge of the sensor.
 17. Asensing system comprising a sensor according to claim 1, and a sensingapparatus comprising a first contactor adapted to effect electricalcontact with the first contact area.
 18. A sensing system according toclaim 17, further comprising a second contactor adapted to effectelectrical contact with a second contact area, wherein a second cut-outportion extends through said first insulating substrate and a spacer toexpose the second contact area on the second insulating substrate.
 19. Asensing system according to claim 17 wherein the first contactor isresiliently biased to extend through the first cut-out portion to makecontact with the first contact area.
 20. A sensing system according toclaim 17 wherein the first contactor is adapted for click engagementwith the first cut-out portion.
 21. A sensing system according to claim18 wherein the second contactor is resiliently biased to extend throughthe second cut-out portion to make contact with the second contact area.22. A sensing system according to claim 18 wherein the second contactoris adapted for click engagement with the second cut-out portion.